Carburetters fitted to internal combustion engines

ABSTRACT

A constant depression or velocity carburetter incorporates an enriching device which acts to increase fuel enrichment with decreasing engine temperature. The carburetter can also include a manifold depression sensor which additionally acts to increase fuel enrichment with decreasing manifold depression.

United States Patent 11 1 Swatman 5] Nov. 4, 1975 CARBURETTERS FITTED TOINTERNAL 3,460,814 8/1969 0116111 261/44 R COMBUSTION ENGINES 3,576,3154/1971 Sutton 123/180 R X 3,677,241 7/1972 Gele et a1. 1 1 261/50 A XInventor Peter Phlllimflre n, Sclihull. 3,746,321 7/1973 DePontac 261/50A England 3,835,831 9/1974 Ross 123/180 R X [73] Assignee: BritishLeyland (Austin-Morris) FOREIGN PATENTS OR APPLICATIONS Limited,Birmingham England 335,680 2/1936 Italy 123/180 R [22] Filed: Jan. 25,1974 Primary Examiner-Tim R. Miles 1 1 pp N062 36,650 AssistantExaminer-William Cuchlinski, Jr.

Attorney, Agent, or Firm-Brisebois & Kruger [52] US. Cl. 261/39 B;123/1875 R; 261/39 E;

261/44 R; 261/D1G. s 1 1 ABSTRACT [51 1 Int. C1. FOZM 1/12 A constantdepression or velocity carburetter incorpo- [58] Field of Search. 261/44R, 39 D, 39 B, DIG. 1, rates an enriching device which acts to increasefuel 26l/D1G. 8, 39 E, 50 A; 123/180 A, 187.5 R enrichment withdecreasing engine temperature. The carburetter can also include amanifold depression [56] References Cited sensor which additionally actsto increase fuel enrich- UNITED STATES PATENTS ment with decreasingmanifold depression. 3,285.585 l 1/1966 Mennesson .1 261/50 A X 4Claims, 2 Drawing Figures l i l US. Patent Nov. 4, 1975 Sheet 1 of 2U.S. Patent Nov. 4, 1975 Sheet 2 of2 3,917,760

CARBURETTERS FITTED TO INTERNAL COMBUSTION ENGINES This inventionrelates to carburetters fitted to inter nal combustion engines either ofthe constant depression or constant velocity type. Both types arecharacterised by having a region of depression of several inches ofwater within the carburetter (referred to subsequently as the constantdepression region). The depression in the constant depression region isused to maintain fuel flow into an air stream passing a jet fed withfuel from a flow chamber or other constant fuel level device open toatmospheric pressure. Downstream of the jet a throttle disc is used togovern the total air/fuel mixture flow.

According to the present invention a carburetter of the constantdepression or constant velocity type having a region of constantdepression within the carburet ter includes:

a. a temperature-sensitive device adapted to provide an output signalwhich varies from a first to a second value in inverse proportion toengine operating temperature, the first value corresponding to normalengine operating temperature, the second value corresponding to a lowengine operating temperature; and

b. an enrichment means adapted, in response to the output signal, tocontrol the degree of enrichment of fuel mixture leaving the carburetterthe variation of output signal from the first to the second valuecausing the degree of enrichment to increase; and the variation of theoutput signal from the second to the first value causing the degree ofenrichment to decrease.

The purpose of the invention is to provide a means of enrichment of thenormal mixture metered by the carburetter for engine cold start andduring warm up.

In a preferred form of the invention engine manifold depression sensingmeans are provided adapted to cause the output signal to be varied ininverse proportion to the engine manifold depression. Preferably thetemperature sensitive device includes a depression control valve whichprovides as output signal a depression varying from a small or zeroamount as first value to a larger amount of several inches water gaugeas second value.

The invention also encompasses a vehicle fuel system including acarburetter according to the present invention and also a motor vehicleincoporating such a fuel system.

The carburetter of the invention essentially consists of a temperaturesensitive device which is a depression control valve which transmits adepression which is nil at normal engine operating temperatures andwhich in creases as the engine temperature gets colder and which mayalso be subject to the influence ofinlet manifold depression so that thedepression signalled by the device increases as manifold depressiondecreases. the source of the depression to the depression control valvebeing manifold depression. The device is so arranged that the maximumdepression signalled is somewhat less than the minimum manifolddepression when the engine is on full load. For example when the sensortemperature is 50C the depression could be min. water gauge and when 30C8 min. water gauge.

The depression thus controlled is transmitted via a flexible small borepipe to operate an enrichment device which can take various forms. Itmay be part of the carburetter or a separate device feeding into theinduc- 2 tion tract downstream of the throttle disc of the carbu retter.

In each arrangement the depression from the sensor unit is applied to adiaphragm or other pressure sensi tive member of known area loaded by arated spring the diaphragm being mounted in a sealed chamber on one sideand open to atmospheric pressure on the other, the depressiontransmitted causing the diaphragm to assume a given position for a givendepression.

Movement of the diaphragm thus engendered controls the degree ofenrichment and the engine fast idle speed.

In one considered arrangement movement of the diaphragm impartsmovements to a pressure balanced valve which controls the degree ofcommunication be tween the constant depression region of the carburetterand the induction system downstream of the throttle disc. lnitialmovement of the valve opens a limited connection area to provide afaster idling speed than normal at normal mixture ratios. Furthermovement of the valve uncovers a cross drilling or orifice which admitsadditional fuel or rich fuel air mixture into the communication passageon the constant depression side of the zone which enriches the overallmixture passing to the engine. Further movement uncovers successivecross drillings which may be graduated in size to provide an appropriateoverall degree of enrichment for the temperature prevailing.

The area of the communicating port to the manifold may be tailored bymeans ofa profiled orifice arranged so that movement of the valve givesa non-linear opening relationship with its excursion.

An adjustable screw may be provided at the centre of the housing on theatmospheric side of the diaphragm to limit its movement towardsatmosphere and so control communicating port area at zero depressioncondi tions thus providing an idle speed adjustment which re places thenormal idling adjusting screw which limits throttle disc closure.

In another arrangement the sensor unit is used in conjunction with anauxiliary miniature constant depression carburetter tuned so that themixture it provides is akin to the mixture ratios of the maincarburetter at idling air flows but increases in richness withincreasing air flows. The depression from the sensor is then arranged tocontrol the degree of air/mixture communication between the auxiliarycarburetter and the inlet manifold by means of a balanced valve.

The sensor unit can in fact be used to signal any enrichment systemwhich requires virtually zero effort to operate it.

An embodiment of the invention will now be described with reference tothe accompanying drawing of which:

FIG. 1 is a diagrammatic layout of an internal combustion engine andintake system; and

FIG. 2 is a part sectioned view of two components representeddiagrammatically in H6. 1.

FIG. I shows a four cylinder spark ignition engine block ll having anintake manifold 12. The intake manifold 12 is fed fuel mixture from aconstant depression carburetter 13 adapted to draw in air along intake14 from a conventional air filter 15. A temperature sensitive device 16is mounted on block 11 and communi cates with manifold 12 by duct 17 andwith carburetter 13 by duct 18.

FIG. 2 shows in more detail carburetter l3 and device l6. Thecarburetter 13 contains a piston 20 slidable within housing 21. Thepiston carries at its lower end a tapered needle 22 which is movable ina jet 23 the size of whose orifice is regulated by means of needle 22.The jet is disposed on a bridge 24 providing a choke in flow passage 25.Float chamber 26 supplies fuel 27 to jet 23 by an unshown duct in theconventional way. Constant depression region 28 in passage lies betweenbridge 24 and butterfly valve 29. Induction region 30 lies downstream ofvalve 29. Passage 31 opens into constant depression region 28 andpassage 32 into induction region 30. Valve shuttle 33 is slidablydisposed in valve chamber 34. Clearance 32a is defined between the endof shuttle 33 and passage 32. The shuttle 33 is resiliently biassed bycompression spring 35 into contact with one end of push rod 36 whoseother end seats on air-tight resiliently loaded diaphragm 37 definingvolumes 38, 39 within chamber 40 in the lower part of the carburetterbody.

Valve chamber 34 is in communication with passage 32 by way of pressurebalance duct 33a in shuttle 33. Auxiliary passage 44 links annulus 45 topassage 31. The shuttle 33 has around it annular recesses 45, 46.

Volume 39 in chamber 40 is open to ambient atmospheric pressure by wayof vent 47. Volume 38 is coupled to temperature sensitive device 16 bythe duct 18. An air bleed 38a provides restricted communication betweenchamber 38 and, effectively, atmospheric pressure. The temperaturesensitive device 16 comprises a housing 48 secured to the engine block11 and in good heat exchange contact with the engine block water coolingsystem. Diaphragm 49 divides the interior of the housing into a majorvolume 50 open to atmospheric pressure and minor volume 51. Duct 18opens into minor volume 51 from which duct 17, by way of valve seat 52,leads to the intake manifold. A disc valve 53 secured to the diaphragmprovides for isolation of duct 17 from the minor volume 51 when thediaphragm is moved downwardly. Motion of the diaphragm 49 is imparted bya bimetallic spring strip 54 linked to the diaphragm 49 by a link 55.The bimetallic strip 54 has a heating element 56 surrounding itenergisable by a battery 57 on operation of switch 58.

The bimetallic strip 54 senses the temperature in major volume 50 and isarranged to vary the upward load on diaphragm 49 so that the load isgreater when the temperature is lower and less when the temperature ishigher diminishing to zero at a predetermined temperature. Any upwardload on diaphragm 49 causes valve 53 to lift from seat 52 admitting thedepression acting in duct 17 into minor volume 51 where it acts on theeffective area of diaphragm 53 tending to close valve 53. When thedepression acting on the diaphragm 53 creates a downward force equal tothe upward load of bimetallic strip 54 the valve 53 closes. Due to airbleed 38a the depression in volume 51 then gradually falls causing valve53 to open thus again admitting to volume 51 the depression acting induct 17 in this manner maintaining on diaphragm 49 a force which justbalances the load of bimetallic strip 54. Thus the greater the upwardload applied by the bimetallic strip (as the temperature in volume 50falls) the greater will be the depression in volume 51. When thetemperature in volume 50 is such that bimetallic strip 54 exercises noload on diaphragm 49 valve 53 seals against seat 52 isolating volume 51from duct 17. In addition to the spring force exercised by bimetallicstrip 54 on diaphragm 49 a pneumatic load is applied by virtue of thedepression in duct 17 acting on the exposed area of 4 valve 53 inopposition to the load applied by the bimetallic strip thus creating: alower depression in volume 51 with increase in depression in duct 17;and a higher depression in volume 51 with reduction in depression induct 17. The depression in duct 17 is inlet manifold depression so thatas the engine load increases the depression in volume 51 will increaseand vice versa. By selecting a suitable area of valve seat 53 it ispossible to vary the depression created in volume 51 as a function ofengine load as well as temperature.

The device is arranged so that the maximum depression fed into duct 18is somewhat less than the minimum manifold depression when the engine ison full load. Typically when the sensed temperature in major volume 50is 50C the depression is 0 min. water gauge and when the temperature is-30C the depression is 8 min. water gauge.

The modified depression supplied to duct 18 from device 16 is fed tovolume 38 on one side of diaphragm 37. Volume 39 on the opposite side ofdiaphragm 37 is maintained at ambient atmospheric pressure.

Diaphragm 37 takes up a resultant position in response to thetemperature moderated manifold depression from duct 18 and the ambientair pressure. This position is transmitted by way of push rod 36 toshuttle 33. The shuttle 33 serves to control the degree of communicationbetween the constant depression region 28 and the induction region 30and by passing the butterfly valve 29.

The flow of fuel from port 41 to auxiliary passage 44 is regulated bythe degree of overlap of annular recess 45 and port 41 and thedepression acting across the port which is constant depression regiondepression. Likewise communication between passage 31 and passage 32, byway of clearance 32a, is governed by the overlap of annular recess 46and clearance 32a.

With the position of the shuttle 33 as shown in FIG. 2 a limited flow offuel from float chamber 26 to auxiliary passage 44 occurs by way ofannular recess 45 partially overlapping port 41. This limited flowpasses into air/fuel mixture flowing down passage 31 which has alreadyentrained the fuel supplied in a known manner through jet 23. Thesubsequently enriched flow then passes by way of annular recess 46 topassage 32 by way of clearance 32a. In the shuttle position shown theclearance 32a serves to limit the flow of enriched fuel, by-passing thebutterfly valve 29, into induction region 30.

Movement of shuttle 33 to the left under the action of push rod 36increases the overlap of the annular recesses 45, 46 with theircorresponding passages with a consequent increase in mass flow alongpassage 32. Displacement of shuttle 33 to the left occurs withdisplacement of diaphragm 37 to the left as will occur, for example,with increasing depression in volume 38 (cold engine).

Heating element 56 is used to heat the bimetallic strip 54 to improveresponse of the strip with a cold engine. As the engine water coolingsystem heats up the effect of the heating element on the strip will bereduced until the engine coolant temperature control of the strippredominates over that provided by the element 56.

In order to ensure full travel of valve 33 during engine cranking undervery cold start conditions, the slow run adjustable screw on cover 40may be replaced by a solenoid rotation of which effects the initial slowrun stop adjustment. The solenoid is electrically connected via athermal sensitive switch to the starter motor circuit so that thesolenoid is energised coincidental with engagement of the starter.Immediately the solenoid is energised its armature moves so as to movediaphragm 37 push pin 36 and spool valve 33 into a position wheremaximum enrichment is provided.

When the engine fires and the starter circuit is disengaged spool valve33 will return to its normal position of enrichment dictated bytemperature in volume 50 and depression in volume 51.

The thermal sensitive switch is arranged to pass current at atemperature when additional enrichment is required such as 5C and below.

We claim:

I. A vehicle engine fuel system comprising:

1. a temperature-sensitive device adapted to provide an output signalwhich varies from a first to a second value in inverse proportion toengine operating temperature, the first value corresponding to normalengine operating temperature, the second value corresponding to lowengine operating temperature;

2. a carburetter of the constant depression or constant velocity typehaving a housing defining a duct and a throttle disc dividing said ductinto a region of constant depression upstream of said disc and aninduction region downstream of said disc, said carburetter furthercomprising:

a. a passage by-passing said disc and providing communication betweensaid constant depression region and the duct downstream of the throttledisc;

b. enrichment means connected to said temperature-sensitive device andcomprising a plurality of orifices communicating with said passage,which orifices are connected, when open, to admit fuel or a mixture offuel and air into said passage, and a pressure balanced valve in saidpassage which is adapted to control the degree of communication betweensaid constant depression region and said duct downstream of the throttledisc in dependence on the value of said output signal by at leastpartially opening and closing at least one of said orifices.

2. A vehicle engine fuel system as claimed in claim 1 comprising anengine manifold depression sensing means connected to said signalproviding means to vary the output signal in inverse proportion toengine mani fold depression.

3. A vehicle engine fuel system as claimed in claim I in which thetemperature sensitive device includes a depression control valveproviding as the output signal a depression varying from a small or zeroamount as said first value to several inches watergauge as said secondvalue.

4. A vehicle engine fuel system as claimed in claim 1 comprising engineidle speed control means, said control means being connected to providea faster idling speed than normal with the output signal at the firstvalue.

1. A TEMPERATURE-SENSITIVE DEVICE ADAPTED TO PROVIDE AN OUTPUT SIGNALWHICH VARIES FROM A FIRST TO A SECOND VALUE IN INVERSE PROPORTION TOENGINE OPERATING TEMPERATURE, THE FIRST VALUE CORRESPONDING TO NORMALENGINE OPERATING TEMPERATURE, THE SECOND VALUE CORRESPONDING TO LOWENGINE OPERATING TEMPERATURE,
 1. A VEHICLE ENGINE FUEL SYSTEMCOMPRISING::
 2. A CARBURETTER OF THE CONSTANT DEPRESSION OR CONSTANTVELOCITY TYPE HAVING A HOUSING DEFINING A DUCT AND A THROTTLE DISCDIVIDING SAID DUCT INTO A REGION OF CONSTANT DEPRESSION UPSTREAM OF SAIDDISC AND AN INDUCTION REGION DOWNSTREAM OF SAID DISC, SAID CARBURETTERFURTHUR COMPRISING: A. A PASSAGE BY-PASSING SAID DISC PROVIDINGCOMMUNICATION BETWEEN SAID CONSTANT DEPRESSION REGION AND THE DUCTDOWNSTREAM OF THE THROTTLE DISC, B. ENRICHMENT MEANS CONNECTED TO SAIDTEMPERATURE-SENSITIVE DEVICE AND COMPRISING A PLURALITY OF ORIFICESCOMMUNICATING WITH SAID PASSAGE, WHICH ORIFICES ARE CONNECTED,WHEN OPEN,TO ADMIT FUEL OR A MIXTURE OF FUEL AND AIR INTO SAID PASSAGE, AND APRESSURE BALANCED VALVE IN SAID PASSAGE WHICH IS ADAPTED TO CONTROL THEDEGREE OF COMMUNICATION BETWEEN SAID CONSTANT DEPRESSION REGION AND SAIDDUCT DOWNSTREAM OF THE THROATTLE DISC IN DEPENDENCE ON THE VALUE OF SAIDUOTPUT SIGNAL BY AT LEAST PARTIALLY OPENING AND CLOSING AT LEAST ONE OFSAID ORIFICES.
 2. A vehicle engine fuel system as claimed in claim 1comprising an engine manifold depression sensing means connected to saidsignal providing means to vary the output signal in inverse proportionto engine manifold depression.
 2. a carburetter of the constantdepression or constant velocity type having a housing defining a ductand a throttle disc dividing said duct into a region of coNstantdepression upstream of said disc and an induction region downstream ofsaid disc, said carburetter further comprising: a. a passage by-passingsaid disc and providing communication between said constant depressionregion and the duct downstream of the throttle disc; b. enrichment meansconnected to said temperature-sensitive device and comprising aplurality of orifices communicating with said passage, which orificesare connected, when open, to admit fuel or a mixture of fuel and airinto said passage, and a pressure balanced valve in said passage whichis adapted to control the degree of communication between said constantdepression region and said duct downstream of the throttle disc independence on the value of said output signal by at least partiallyopening and closing at least one of said orifices.
 3. A vehicle enginefuel system as claimed in claim 1 in which the temperature sensitivedevice includes a depression control valve providing as the outputsignal a depression varying from a small or zero amount as said firstvalue to several inches watergauge as said second value.
 4. A vehicleengine fuel system as claimed in claim 1 comprising engine idle speedcontrol means, said control means being connected to provide a fasteridling speed than normal with the output signal at the first value.